Excellent Upconversion Luminescence Intensity in Er3+/Yb3+/Mo4+ Triple-Doped Bita7o19 Phosphors

Abstract

BiTa 7 O 19 :Er 3+ /Yb 3+ /Mo 4+ phosphors with excellent upconversion luminescence (UCL) intensity were synthesized by high temperature solid state method. The crystal structure, grain morphology and valence states of molybdenum ions were determined by X-ray diffraction (XRD), field emission scan electronic microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) technologies, respectively, and the UCL properties were studied by spectroscopy under 980 nm laser excitation. The green UCL intensity of BiTa 7 O 19 :0.1Er 3+ /0.4Yb 3+ /0.4Mo 4+ is 1.66 times higher than that of commercial NaYF 4 :Er 3+ /Yb 3+ under 980 nm laser excitation with 18.09 W/cm 2 . The UCL intensity of BiTa 7 O 19 :Er 3+ /Yb 3+ phosphors increased first and then decreased with the increase of 980 nm laser excitation power density (0.38-56.69 W/cm 2 ), while the UCL intensity of BiTa 7 O 19 :Er 3+ /Yb 3+ /Mo 4+ phosphors can keep increasing with the increase of excitation power density. Based upon the luminescence intensity ratio (LIR) technique, the maximum absolute sensitivity (S A ) is 0.01046 K -1 at 401 K. The experiment proved that BiTa 7 O 19 : Er 3+ /Yb 3+ /Mo 4+ phosphors had strong acid and alkali resistance compared with NaYF 4 :Er 3+ /Yb 3+ . It indicates that BiTa 7 O 19 :Er 3+ /Yb 3+ /Mo 4+ can replace NaYF 4 :Er 3+ /Yb 3+ to be applied as luminescence imaging and temperature sensors in complex environments under high 980 nm laser excitation power density.

Keywords: BiTa7O19, Triple-doped, Tantalate, Upconversion luminescence, Temperature sensing